Final answer:
Prions are infectious proteins that cause disease by prompting the misfolding of normal cellular proteins, leading to neurodegenerative conditions.
Step-by-step explanation:
The correct statement about prions is that they cause abnormal folding of normal cellular proteins. Prions are infectious agents that are composed entirely of proteins and contain no nucleic acids - neither DNA nor RNA. They replicate by inducing the abnormal folding of normal cellular proteins known as PrPC into a misfolded form referred to as PrPSC. These abnormal prions aggregate in brain tissue and lead to a variety of neurodegenerative diseases in animals and humans, such as mad cow disease and Creutzfeldt-Jakob disease.